Forked from  issue 779267 

If VMTestStage is retried on betty-release for whatever reason, the second attempt at devmode_test fails in mount_gpt_image.sh

Even though the first attempt had passed!

This suggests that devmode_test is somehow changing the state of the source image such that it can not be run twice.

Example run: https://uberchromegw.corp.google.com/i/chromiumos.tryserver/builders/release/builds/16922

VMTestStage 1 failed for an unrelated reason.
VMTestSTage 2 failed because devmode_test died.

Preliminary poking around suggests that the failure in attempt 1 was not the cause of a corrupted image (it cleanly shutdown KVM).